congressman jesse jackson jr. resigned today. two weeks ago he was re-elected despite disappearing from public view days earlier. we learned he was being treated for a disease, now, a cloud. there is a federal investigation. here is nbc's kelly o'donnell. >> reporter: today, a once promising political career is officially over, with an end marked by spiraling legal troubles, jesse jr., the son of the famed civil rights leader, gave up his seat in congress after 17 years in a letter, he wrote in part, my health issues and treatment have become incompatible with service in the house of representatives. jackson has been in the hospital on and off since june for treatment of bipolar disorder, seen here while a patient at the mayo clinic. today, cook county officials are weighing options for a special election to replace jackson. >> and i think he feels that the district he represents, somebody should be there in a healthier condition than he is. >> reporter: but jackson makes striking admissions about his mistakes, talking to the jus